The “550 5.7.1 [CS] Message blocked Spam” error with MailChannels can be frustrating; however, it doesn’t mean your domain is permanently blocked. By applying authentication, cleaning mailing lists, and following safe sending practices, resolving a MailChannels spam message block can be quick and prevent future blocks.
This guide will help you understand this error and how to prevent it from happening.
What Does This Error Mean?
If you see the “550 5.7.1 [CS] Message blocked Spam” error, MailChannels detected something in your email that looked like spam. This could be your content, your list quality, or even a compromised account.
Why MailChannels Blocks Emails
- Sending to invalid or inactive addresses.
- Messages with spam-like wording, attachments, or suspicious links.
- Accounts compromised by malware or weak passwords.
- Missing or misconfigured SPF, DKIM, or DMARC.
- High complaint rates from recipients.
How to Fix the Error
1. Check the Content
Remove spammy phrases, suspicious links, or large attachments.
3. Secure Your Account
Change your password, update your operating system, and run antivirus scans.
4. Clean Your Mailing List
Remove invalid addresses or unengaged contacts.
5. Retry Sending
Once fixes are applied, retry the message.
Tips to Reduce Spam Flags
1. Maintaining Mail Reputation
- Don’t write emails without a subject line.
- Don’t write subject lines in ALL IN CAPS.
- Don’t plead with people to “Open Me!”
- Don’t deceive readers with a false promise.
- Don’t give away everything in your subject line (Do not make your subject line too long).
- Don’t use one word like “Hi!” as your subject line.
- Skip the punctuation!!!
- Don’t add Re: to your subject line to deceive readers.
- Avoid using blacklisted URLs or suspicious/bad attachments in the mails.
2. Scanning Devices with Antivirus Software
Recommended Antivirus Solutions (Paid)
Free Antivirus Solutions
- AVG Free (For PC)
- AVG Free (For All Devices)
- Microsoft Defender (built into Windows)
- TotalAV Free
- Lavasoft
TIP: Choose a solution that provides real-time scanning, phishing protection, and suspicious website alerts.
3. Consider Changing Your Email Password
Sometimes, a good practice is to keep your email passwords refreshed. This, however, means ensuring that you make changes across devices, and not just for Webmail.
How to Prevent Future Blocks
- Use double opt-in to confirm subscribers.
- Keep lists updated and remove invalid recipients regularly.
- Write clear, relevant subject lines (avoid “FREE $$$” or all caps).
- Don’t send bulk messages without warming up gradually.
- Regularly monitor DMARC and MailChannels reports.
When to Contact 1-grid Support
If you’ve followed these steps and still experience MailChannels blocks, contact our Support Team.
Provide the following (with screenshots, where possible):
- The full bounce-back message.
- Steps you’ve already tried.
- Details of your SPF, DKIM, and DMARC setup.
FAQs
Is my domain blacklisted if I see this error?
Not necessarily. This error is usually temporary and can be resolved by fixing content or authentication.
Can MailChannels blocks happen even with small email volumes?
Yes, if messages look suspicious or are sent to invalid recipients.
Will SPF, DKIM, and DMARC prevent all blocks?
They prevent many, but sending practices also play a big role.
How fast can I resume sending after fixing issues?
In most cases, once problems are resolved, sending resumes automatically.
Can 1-grid unblock me if this was a false positive?
Yes, 1-grid can escalate the issue to MailChannels for review.
Additional Resources
MailChannels Error Codes and How to Fix Them
How to Resolve MailChannels Error 550 “Too many invalid recipients”
MailChannels FAQs
Updating My Password FAQs
Top 10 Common Email Issues and How to Resolve Them
Setting Up Email in Outlook via Windows Control Panel
How to Set Up Email on Android for Your 1-grid Email Accounts
Settings to Configure Your 1-grid Email Accounts Across Devices
Resolving Email Error Messages When Sending to Gmail Accounts
What is IP Blacklisting?
How Do I Check if My IP is Blacklisted?
SpamTitan: How to Blacklist an Email Address or Domain
What Is Email Spoofing? How It Works and How to Protect Yourself
How to Spot a Scam Email
Email Headers FAQs
Email FAQs
How to Enable DKIM and SPF on Your Mail Domain
Why SSL? The Purpose of Using SSL Certificates
What is a Domain Name Server (DNS)?
How to Update Your Domain’s Nameservers at 1-grid
SpamTitan FAQs
Need Additional Support?
We’re Here to Help:
Preventing emails from being blocked by MailChannels as a spam block doesn’t have to feel technical with this easy-to-reference guide. Stuck? Contact our Support Team for clarity and guidance (https://1grid.co.za/contact-us/). We’re ready to see how we can help!